Technical Field
The present disclosure relates generally to the field of resource constrained operational planning methods and systems, with horizontal well development planning serving as a non-limiting example.
Background Art
“Critical path method” is a well-established planning and scheduling method. Planning/scheduling tools, such as the software known under the trade designation PRIMAVERA″, and similar planning/scheduling tools use a critical path method (“CPM”) engine to calculate total and free float for a project, defined by the Project Management Institute as: “a temporary endeavor with defined scope . . . ”. In typical project planning, the scope of the deliverable (project) is known and understood upfront. This allows the CPM engine to perform a forward and backward pass. The forward pass calculates the earliest an activity can start or finish based on its predecessors. The backward pass starts from the end of the project and works backward to calculate the latest an activity can start and finish (without impacting the calculated end date for the project—deterministic). The path of 0 float is the critical path, to which a day of delay on an activity results in a day delay to the project. Resource analysis is also typically approached with a different intention. For instance, during resource analysis, any activities that are delayed due to resource un-availability could potentially have more resources allocated to compress the schedule.
No current tools address the unique operational challenges of horizontal oil & gas well developments, referred to herein as simply “horizontal well developments”, which typically, but not necessarily are in shales. With each horizontal well development comprising multiple “stages”, each horizontal well is effectively 10-20 “normal” vertical wells. The volumes of consumables used to drill and complete a horizontal well can be many times that of a typical vertical well. The directional nature of the well also creates a spacing question. In a typical vertical development, spacing is based on assuming somewhat omnidirectional reservoir drainage. A grid can be established allowing for a reasonably accurate count of wells to plan by. Horizontal wells must set a maximum well length (completable lateral), and a distance between the wells. The length and spacing variables affect the total number of wells required to develop the field considerably. Reducing the spacing between the wells by half would roughly double the number of wells required. For multi-well pad operations, it also increases the amount of time a drilling rig remains in an area. Typical day rates for drilling rigs now (mid-2012) range from tens to hundreds of thousands of $US/day.
Traditional logic-based planning requires that a predecessor activity is completed before its successor can begin. This is applied for the activities that define the drill & equip of a well, but not for the order the wells will be developed. Since the location and number of future wells is unknown, it is impossible to use logic to plan effectively. Predecessor/successor logic can be used for well pads (i.e., all wells on a pad must be drilled before the first well can be completed) but resource priority is used to determine the order of the activity. Since each well has it's own critical path, and the “project finish” is only the latest well in the schedule, the true “critical path” has little meaning when using scheduling software for resource based operational planning/scheduling. CPM scheduling methods and tools are not ideally suited for this type of planning, because the goals are different.
Simultaneous Operations (“SIMOPS”) is a very necessary planning consideration. Drilling rigs must increase mud weight to hold back induced pressure from a nearby frac crew. The risk being that the rig can not “mud up” fast enough, or any uncased zones already drilled through would not be able to hold up to the increased mud weight, resulting in well control issues ranging from loss of circulation to a blowout. Planning to keep enough distance between rigs and frac crews is necessary. In addition to the “point in time” spatial conflict, the residual pressure can also affect future drilling operations. There is an “ideal” time to return to an area to resume drilling after frac operations have finished.
Having identified the above problems, it would be an advance in the resource planning art if methods, systems, and computer-readable media were available to reduce or overcome some or all of the above problems seen in currently available planning methods and systems. More specifically, it would be an advance in the resource planning art if methods, systems, and computer-readable media were available to enable presently known or future CPM planning/scheduling software to perform resource constrained operational planning, for example, but not limited to, horizontal well development planning (upstream activity).